A lighting apparatus with a number of light emitting diodes mounted on a conductive plate is proposed as a lighting apparatus employing light emitting diodes. For example, in a lighting apparatus shown in Patent Document 1, a cooling member is connected to a conductive plate in a side where light emitting diodes are not mounted, thus, heat dissipation of light emitting diodes is accelerated to provide a lighting apparatus that can emit high power light. In addition, in order to further improve heat dissipation, a cooling fluid is circulated in the cooling member.
Furthermore, in a vacuum fluorescence tube shown in Patent Document 2, for example, an anode of a conductor with a phosphor layer coated thereon, and a cathode that opposes to the anode are provided in a vacuum case. This vacuum fluorescence tube is used as a vacuum fluorescence tube of a light source for a facsimile. In this case, a part of the anode with the phosphor layer coated thereon extends outwardly of the vacuum case as an extending portion. The extending portion serves as a cooling portion that is exposed to the outside air. In this fluorescent tube, the anode with the phosphor layer coated thereon is made of a heat conductive metal such that the aforementioned cooling portion aids heat dissipation, thus, heat generation of the phosphor layer that is coated can be reduced. Accordingly, in the vacuum fluorescence tube, deterioration of the phosphor is prevented, thus, it is possible to improve luminous efficiency and to maintain high-brightness light emission.
Typical cooling means in a heat sink used against heat dissipation of a heating element, such as semiconductor device is divided into two types, one is passive cooling means, and another one is active cooling means. In the former, heat of the heat generating element is dissipated by using a heat sink with a high heat capacity. In the latte, heat is taken away by flowing cooling water in a heat sink with a heat generating element mounted thereon. In recent years, since semiconductor apparatuses are required to further increase output or brightness, active cooling means is preferably employed in terms of cooling efficiency.
In semiconductor apparatuses employing passive cooling means, for example, an infrared semiconductor laser array has been provided one to several tens watts (W) of light output. The semiconductor laser array refers to an array that has a plurality of resonators arranged on a single semiconductor crystal, or to an array that has respective resonators arranged on a plurality of separated semiconductor crystals.
Moreover, a semiconductor laser array with stack structure has been provided several tens to several kilowatts (W) of light output. Active cooling means is employed in this type of semiconductor apparatus with stack structure. For example, Patent Document 3 has been proposed a technique that cools directly under a semiconductor laser array with a water path provided in a heat sink. A plurality of very small holes that are formed by narrowing the water path are provided in the water path so as to spray pressurized fluid toward directly below heat generating elements. The fluid is vigorously sprayed toward directly below the semiconductor laser array, thus, it is possible to improve heat transmission efficiency. In the structure of this semiconductor apparatus, the water path is designed such that the fluid is incident upon the heat dissipation surface of the heat generating element such as semiconductor laser at substantially right angle.                Patent Document 1: Japanese Laid-Open Patent Publication TOKUHYOU No. 2002-544673        Patent Document 2: Japanese Laid-Open Patent Publication TOKUKAI No. SHO 59-161966        Patent Document 3: Japanese Laid-Open Patent Publication TOKUKAI No. HEI 8-139479        